In this work, the trend in the performance of carbon fiber (CF) and its composite during self-polymerization of polydopamine (PDA) at carbon fiber surface was investigated by varying the self-polymerization time of dopamine in an aqueous solution. Research has shown that the PDA coating elevated the surface roughness and polarity of the inert fiber. The tensile strength of single carbon fiber was significantly improved, especially after 9 h of polydopamine self-polymerization, increasing by 18.64% compared with that of desized carbon fiber. Moreover, the interlaminar shear strength (ILSS) of CF-PDA9-based composites was 35.06% higher than that of desized CF-based composites. This research will provide a deep insight into the thickness and activated ingredients of dopamine oxidation and self-polymerization on interfacial compatibility of carbon fiber/epoxy resin composites.

Optimized interfacial compatibility of carbon fiber and epoxy resin via controllable thickness and activated ingredients of polydopamine layer
    Abstract 
    Graphical abstract
    1 Introduction
    2 Experiments
        2.1 Materials
        2.2 Self-polymerization of PDA on the silicon wafer and carbon fiber surface
        2.3 Preparation of modified CFepoxy resin composites
        2.4 Characterizations of PDA-modified carbon fiber
    3 Results and discussion
    4 Conclusion
    Acknowledgements 
    References

• Dongliang Wu(School of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, People’s Republic of China)
• Yuxuan Xing(School of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, People’s Republic of China)
• Denglu Zhang(Linyi Luyi Textile Co., Ltd., Linyi, People’s Republic of China)
• Zhenna Hao(School of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, People’s Republic of China)
• Qi Dong(School of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, People’s Republic of China)
• Yongqin Han(School of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, People’s Republic of China)
• Lei Liu(School of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, People’s Republic of China)
• Maoju Wang(Qingdao Huashijie Environment Technology Co., Ltd., Qingdao, People’s Republic of China)
• Ruliang Zhang(School of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, People’s Republic of China) Corresponding author